Various disease processes can impair the proper functioning of one or more of valves of human heart. These include degenerative processes (e.g., Barlow's Disease, fibroelastic deficiency), inflammatory processes (e.g., Rheumatic Heart Disease) and infectious processes (e.g., endocarditis). In addition, damage to the ventricle from prior heart attacks (i.e., myocardial infarction secondary to coronary artery disease) or other heart diseases (e.g., cardiomyopathy) can distort the valve's geometry causing it to dysfunction.
The benefits of valve repair over replacement are well established in the cardiac surgical literature in all types of valve dysfunction and in nearly all disease states. Patients undergoing valve repair have been shown to live longer, with better preservation of cardiac function. The vast majority of patients with mitral or tricuspid regurgitation can have their valves successfully repaired instead of replaced. The likelihood of a successful repair, however, is highly dependent on the skill, knowledge and experience of the individual surgeon. Although most surgeons are comfortable performing simple valve repairs (annuloplasty rings, limited leaflet resections, etc.), many rarely perform valve repairs and only a small minority of surgeons are comfortable at more complex valve repairs. Most surgeons have inadequate knowledge and training in these techniques and, even if they had the technical ability, they do not encounter enough patients to feel comfortable with complex cases. This variability in surgical skill is reflected in the wide range of valve repair rates among different centers. High-volume, experienced centers routinely report valve repair rates over 90% while the national average is only 20-30%.
Since they involve work inside the heart chambers, conventional procedures for replacing or repairing cardiac valves require the use of the heart-lung machine (cardiopulmonary bypass) and stopping the heart by clamping the ascending aorta and perfusing it with high-potassium solution (cardioplegic arrest). Although most patients tolerate limited periods of cardiopulmonary bypass and cardiac arrest well, these maneuvers are known to adversely affect all organ systems. The most common complications of cardiopulmonary bypass and cardiac arrest are stroke, myocardial “stunning” or damage, respiratory failure, kidney failure, bleeding and generalized inflammation. If severe, these complications can lead to permanent disability or death. The risk of these complications is directly related to the amount of time the patient is on the heart-lung machine (“pump time”) and the amount of time the heart is stopped (“crossclamp time”). Although the safe windows for pump time and cross clamp time depend on individual patient characteristics (age, cardiac reserve, comorbid conditions, etc.), pump times over 4 hours and clamp times over 3 hours can be concerning even in young, relatively healthy patients. Complex valve repairs can push these time limits even in the most experienced hands. Even if he or she is fairly well versed in the principles of mitral valve repair, a less experienced surgeon is often reluctant to spend 3 hours trying to repair a valve since, if the repair is unsuccessful, he or she will have to spend up to an additional hour replacing the valve. Thus, time is a major factor in deterring surgeons from offering the benefits of valve repair over replacement to more patients. Devices and techniques which simplify and expedite valve repair would go a long way to eliminating this deterrent.
Within recent years, there has been a movement to perform many cardiac surgical procedures “minimally invasively” using smaller incisions and innovative cardiopulmonary bypass protocols. The purported benefits of these approaches include less pain, less trauma and more rapid recovery. However the use of these minimally invasive procedures has been limited to a handful of surgeons at specialized centers. Even in their hands, the most complex valve repairs cannot be performed since dexterity is limited and the whole procedure moves more slowly. Devices and techniques which simplify valve repair have the potential to greatly increase the use of minimally invasive techniques which would significantly benefit patients.